Telephone receiver



Oct.. 12 1926.

L. L `JONES TELEPHONE RECEIVER Z.. fw

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BY l v MfWMMTToRNEx/c zov Patented @et l2, lg.

L. JONES, OF NEW" YORK, N. Y., SSIGNOR TO POWERFONE COMPANY, 0F NEW iRK, Y., A PARTHERSHISP COMPOSED JNES, AND ALLEN D. GARDWELL.

F WILLIAM DUBILIER, LESTER L.

' TELEPHONE RECEIVIEJR.

application mea may a, ie'aav serial iro. 557,838.

The invention relates to an instrument for transforming electricalimpulses into sound waves, such as telephone receivers `and thelike,.and the features of the invention, although of quite generalapplication, are particularlyuseful in connection with receivers"operating with substantial amounts of power, and adapted to producesound wavesv of large volume.-

One object of the invention is to provide a receiver of the above typewherein the magnetic circuitsare so related aswto -be highly sensitivetochanges in electrical impulses impressed thereon, whereby the soundwave generating diaphragm which is operated by changes in the magneticcircuit. may lbev caused to produce distinctly and sharply the soundwaves corresponding to different electrical impulses.

Another object is to construct the instrument so as to permit thearmature vwhich operates the sound-producing diaphragm,

to be intimately related to the pole pieces vof the magnets with whichit cooperates, and yet without danger that thev slight spacing betweenVsuch armature .and the pole pieces will be likely to cause stickingofthe armature between or against the same. It is also desired to employ amagnet structure ,which will decrease the length of the armature iuXpath by permitting the pole pieces which influence such armature, to beset very closetogether.'

'The invention also aims to enable the use in receivers of the abovecharacter of diaphragms whichV are exceedingly thin, flex`- ible and of,light weight, and therefore capable of responding sensitively to changesvin the magnetic field, but under. such -conditions that a large gapneed not be em ployed in connection with the diaphragm to insure thatthe impulses are transmitted to. a relatively large area thereof, or toprevent sticking against' thegpole pieces.

Another object is 4tosegregate,4 .soto speak, the variablemagneticcircuit of the receiver froin'the .constant magnetic circuitthereof so as to enable each of such circuits .to react eihciently uponthe'diaphragm, and `eliminate losses which might-occur .due tointeraction between such circuits.

Another Objectis to provide a receiver wherein a sound-'producingdiaphragm and an armature. for actuating same are so combined andrelated to the magnetic circuits of the receiver that the magneticforces` will produce a maximum effect upon the diaphragm. A y

c The invention also aims to permit energy transfers from thesoundproducing .diaphragm t'o the surrounding air without the generationof objectionable resonance tones,

by employing a diaphragm which 'communi Cates with the outer-'airthrough an opening of relatively large area. y

Further objects and advantages of the invention will be in part obviousand in part speciiically pointed out in the description hereinaftercontained, which, taken incon- Y ing operatively related to the parts ofthe receiver which appear in Figs. l to E.v

Fig. 5 is a diagrammatic view illustrating a mo'dication of certainfeatures of the invention. I

Referring to the drawings, a telephone receiver is illustrated 'having apermanent magnetic circuit embodyingga magnetl,

-which may be of any convenient shape, and

which in the present instance is shown as of the horseshoe type, havingVpoles 2 `and 3, between which are located pole pieces/t vand 5 lwhichwill .belmore Ifully described hereinafter. In the' illustratedembodiment of the invention the-magneto motive .force of theabove-mentioned magnetic circuit is obtained entirely from the ermanentmagnet l, which ispreferably otp relatively large power, whereby. theflux emanating therefrom constitutes a relatively large fraction ofthetotal ux which influences the soundproducing diaphragmof thereceiver.

In connection with the above-mentioned magnetic circuitthere is employeda variable magnetic circuit, which in the present yform is made up ofleg 6 integral with the pole ico piece previously described, andextending across the inne'r face of pole piece 3 of the l permanentmagnet, and a further magnetic permanent or constant-magnetic circuit,and, the variable or branch ,magnetic circuit' which is affected by`coil 9. This last-mentioned circuit is later referred to as being inparallel with the permanent or Aconstant magnetic circuit, sincepermanent flux passes, for example, from pole 2 to pole pieces 4 and 7,and across gap 10 to pole piece 5 and pole 3; it should be noted howeverthat the above arrangement also provides a parallel path for thepermanent fiux which includes elements 2, 4,7, 8, 6 and 3 and in aparallel path 7, 8--14, 6, 3.

The magnetic system is so arranged as to maintain substantially constantiux in the magnetic circuit, comprising magnet 1, by including a portionof relatively hi'gh reluctance in such circuit, which is in series withpole pieces 5 and 7, and' the variable magnetic circuit. As shown inFig. 1, thisA portion of high reluctance takes the form of aflux-limiting gap 11 interposed between the ole pieces 4 and 5, whichgaplimits the totalD amount of flux passing through the permanentmagnetic circuit, and xes the I amount of permanent flux passing acrossthe ga 11, regardless of the changesl in the variab e ma netic circuitwhich are produced by coil)r 9.

The provision of a high reluctance portion such as gap 11, in thepermanent magnetic circuit, opposes any tendency of the iuX from thevariable magnetic circuit passing around through permanent magnet 1,whereby hysteresis and eddy current losses are avoided in the magnet 1,due either to changes inthe permanent fiux, or thepassage of fluxtherethrough which is generated by coil 9. Thus with circuits of theabove nature the pole pieces 5 and 7 and the ele-l ments 6 and Smay belaminated as indicated in Fig. 2, to cut down the losses in the variablemagnetic circuit, but the permanent magnetic circuit, which may not bevery readily constructed of laminatedv pieces, will not vcause increasedlosses due to flux variations therein.

. Fig. 5 illustrates a modication of this idea, wherein a permanentmagnet 1I1 is provided with `poles `2a and 3, and pole pieces 7n and 4carrying f1uX-varying coils 9El and 9, which are mounted on the poles 2aand 3"' respectively, together with legs 82L and 6*1 extending betweenthe poles 2a and 3a to provide a shunt path for the variable magneticflux produced byy coils 9cl and 9". In this instance the flux passingaround through magnet 1a is limited by means of short circuited loops 12and 13 of copper or the like enclosing the poles 2a and 3a, whichmembers 12 and 13 oppose the passage of variable ilux around through themagnet 1.

.Referring again to the embodiment of the invention illustrated in Figs.1 to 3, the variable magnetic circuit is also provided with a portion ofhigh reluctance, such as air gap 14, in the present instance interposedbetween the legs 6 and 8 previously described, to balance the iuxpassing through the permanent magnetic-circuit, and to insurethat aproper proportion thereof will pass across the gap l()V between polepieces 7 and 5.

"It is obvious that the short-circuiting means such as the loops 12 and130i1 copper or the like, shown in Figure 5, may be applied to theembodiment of the invention illustrated in Figures 1 to 3. Here theshortcircuiting loops may consist of rcopper or the like arranged in theposition shown in Figures 1 and 2 and indicated by the numerals 12u.

It will be noted that coil 9, being located in theshunt part of thevariable circuit, has no effect upon the permanent flux which passesacross the gap 11, but serves to divert a variable portion of the per*manent fiuX through gaps 10 and furthermore this coil being located inthe shunt part of such circuit does not require a spacing be- 'tween thepole pieces 5 and 7 conforming to theldimensions of thecoil. In otherwords the pole pieces 5 and 7 may be set very close together, so as toreduce the reluctance of armature 15 and its weight, as contrasted to astructure, for examp e, as illustrated in Fig. 5, where thepole pieces 4and 7l1 are spaced a distancecqual to or greater than the diameter ofone of coils 9a or 9b.

The disposition of the coil 9a in the shunt partof the variable magneticcircuit also avoids thenecessity of employing two coils of this nature,as has oftembeen done.

In the illustrated embodiment of the invention a separate armature 15 isdisposed adjacent the pole pieces 5 and 7 and connected to the diaphragm16 (Fig. 1) to move the latter in accordance with the variations in fluxbetween pole pieces 5 and 7. The armature 15 is enabled to be spacedviery slightly from the pole pieces, as hereinafter described in greaterdetail, andas such pole pieces are set very close together, the lengthand reluctance of the armature, are very small. For example, thearmature air gap may be ten thousandths of an inch, and the Lacassedistance betweenfadjacent surfaces of the polepieces and 7 need not begreater than sixty thousandths of an inch with; the armas.

mensions so related to the magnetic forces acting thereon that the ratiovofmagneticpull tothe weight of the armature may be substantially at amaximum. The condition is substantially satisiied by the lequation lL=1/ 8 l M G, where L is the dimension of Athe armature in thedirectionwof the flux, T the thickness of the armature,l\ thepermeability of the armature, and G the normal distance between thearmature and the pole pieces. Thus the magnetic lux passing through thearmature will be relatively large, while the mass or weight of thearmature is relatively small, resulting in the ap'- plication ofefficient forces to the diaphragm 1G to influence the same. f

The pole pieces 5 and l7 are also preferably so shaped and related tothe remainder of the magnetic structure' as to concentrate the iiuxbetween the polepieees, in the region of the armature 15.. As shown, thesurface 5al of the pole piece 5, which opposes pole piece 7, is beveledback, or tapered toward the Y armature, while the surface/f7? ofthe polepiece 7 is also cutaway to Adirect the major portion of the lux in pole'piece 7, through f the opposite portion of such pole'piec'e which '35is adjacent'the armature.' As appearsin l Fig. 1, the cross sectionalarea ofthe pole pieces 5 and 7 furthermore preferably is made relativelysmall, with respect to thev remaining magnetic parts of the magneticcircuits including such pole pieces, whereby the flux density in thepole piecesis relatively greater or more concentrated. It is alsopreferred toemploy a diaphragm 16, the effective weight in motion ofwhich is substantially equal to the weight of the armature. If a heavier'diaphragm is employed the motionimparted thereto when the armature isactuated by the magnetic forces, is relatively small, while if thediaphragm is too light, the forces of the magnetic pull are transmittedonlyto a relatively small fraction of the area thereof.

In order to permit the -use of a very small air gap between the armature15 and the pole pieces. 5 and 7, without danger of the armaturesnappingover against or sticking to the pole pieces, -it is also preferred toapply .external forces to the armature 1.5, urging the same in thedirection ofthe magnetic"A pull. In the present instance, the armatureis connected to diaphragin 16 at its intermediate portion, and suitablemeans. such as metallic threads '16a (Figs2 and 3) are afxed to the endsof the armature and placed 05 under tension as bysuitablebinding'scr'ews 17. Then the screws 17 are tightened up to apply tensionto the threads 16a, the armar,

ture 15 is pulled toward the pole pieces, and the diaphragm 16 is flexedas indicated in Fig. l. Threads lliejin the plane of the' gap when thearmature touches the poles .so'

that they no longer urgel armature towards A l pole. i The combinationof this rapidlydisappearing gap closing force with the dia'- phragmreaction, presents a rapidly 'increaslng resistance to further flexure,thus coun- 'teracting the tendency of the increased magnetic pull as thearmature approaches the pole pieces, to stick the armature against thesame. Preferably the forces exerted by the threads l upon the armaturewhen the ar,-

'mature is inits operating position are greater than the maximummagnetic pull which may be imposed-upon the same for any ar mature gaplength, to insure vthe maintenance of 'the air gap between the armatureand the pole pieces under all conditions..

Where an armature spaced from both pole pieces is employed, as in thecase of the'illustratedl embodiment, it is preferred to so connect thearmature to the diaphragm'l as to permit equalization of forces Vappliedthereto by the threads or members 16a. In the present instance, a hookedrod 18, fixed to' the diaphragm, engages with a bridle 19, having itsend fastened to the armaturein Such manner that the stresses, imposedupon vthe opposite ends ofthe armature by threads 1621 become balanced,to 'provide against one end of the armature snapping-over against itscorresponding pole piece due to unequal stress distribution.

The initial lexure of diaphragm 16 asy above described, also permits theeliicient vuse of a large diaphragm, 'which diaphragm may yet be fverythin, and' therefore flexible and sensitive, and of4 lightweight. Ifathin and flexible diaphragm -be employed eol underordinarycircumstances, since the diaphragm yields readily,` a large'airfgap might have to be 'employed to .prevent the diaphragm or itsarmature'from snapping over or sticking to the. pole pieces, andfurther-- more the flexibility of the diaphragm might bring about theresult that the magnetic attraction .of the armature would affect only'a' relatively small part of the area of the'diaphragm. But if thediaphragm be initially flexed, a very small air gap nevertheless may beVemployed as above described, and

the tension upon the material of .the'dia-A phragm insures that themagnetic forces will be transmittedover the major portion izo of itsarea. .The diaphragm may beco'- structed of very thin steel, and theinvention 'also makes possible the use of readily stretchable materialssuch as paper, or hide,

sincethe tension on the diaphragm makes it taut to a much greater extentthan would be possible merely by magnetic pull. Thus occur if a verythin. iexible diaphragm were.

the higher tones (those above two thousand cycles) are vnot lost, whichotherwise might used.

lAs isillustrated in Fig. 4, the magnet structure-and diaphragm may bemounted within a suitable casin 20, the edges of the diaphragm beingheld etween the adjacent wall of-the casing and a ring 21 overlyingA thesame. The diaphragm 16 is also preferably placed in communication withthe outer air either directly or through a horn or the like 22, havingan opening substantially equal in area to the area of the diaphragm;thus resonance chambers are avoided, permitting the energy of thediaphragm lto be transferred to the .surrounding air without thegeneration of resonance tones.

While aspecific embodiment has been disclosed, it will be obvious thatmany changes may be made therein without departing from the principle ofthe invention, as de- `fined in the appended claims.

motive force, a branch magnetic circuit in parallel therewith, a soundreproducing diaphragm, said circuits having pole pieces 4adapted toinfluence said diaphragm, and a coil inductvely related to said branchcircuit, said branch circuit having portions of high reluctance at itsopposite ends separating the saine from the first-mentioned circuit.

3. A telephone receiver comprising a sound reproducing diaphragm, amagnetic circuit, and a branch circuit in parallel therewith, saidcircuits having pole pieces' to influence said diaphragm, the branch'circuit including portions of high reluctance separating it from thefirst mentioned-circuit.

4. A telephone receiver comprising a sound `reproducing diaphragm, amagnetic circuit, a branch circuit in parallel there with, said cicuitshaving pole pieces to influence said diaphragm, the branch circuithaving portions of high reluctance separating it 'from' the rstmentioned circuit, and means forvarying the eiiect of the branchcircuit.

5. A telephone receiver com rising a magnetic circuit of predeterminemagnetic motive force, a branch'.inagnetic circuit in incassa.

parallel therewith, a soundreproducing diaphragm, said circuits havingpole pieces adapted to infiuence said diaphragm, and a coil inductvelyrelated to said branch cirphragm, said circuits having pole piecesadapted to influence said diaphragm, and a coil inductvely related tosaid branch circuit, said irst-mentioned circuit having an air gaptherein in series with said branch circuit. v

7. A 1 telephone receiver comprising a magnetic circuit of predeterminedmagnetic motive force, a branch magnetic circuit,l in paralleltherewith, a sound reproducing diaphragm, said circuits having polepieces adapted to influence said diaphragm, a coil inductvely related tobranch circuit, said first-mentioned circuit including a portion ofrelatively high reluctance in series with said branch circuit, and thebranch circuit also having a portion of relatively high reluctancetherein..

8. A telephone receiver comprising a magnetic circuit, and a branchcircuit in parallel therewith', a sound reproducing diaphragm, saidcircuits having pole pieces to inuence said diaphragm, and said firstcircuit having a portion of relatively high reluctance in series withthe branch circuit.

9. A telephone receiver comprising a flexible diaphragm, pole piecesadapted to in- 1iiuence the same, and balancing means for exerting aforce additional to the magnetic pull from the pole pieces tending toflex said diaphragm in the direction of the magnetic pull, said meansexertin a force on the diaphragm greater than t e maximum magneticpull.v

10. A telephone receiver comprising a l flexiblev diaphragm, an armatureconnected thereto, pole pieces adapted to influence said armature, andbalancing. means to exert a force additional to the magnetic pull fromthe pole pieces tending to urge said armature inthe direction of themagnetic v pull, said means exerting a force on the diaphragm greaterthanthe maximum magnetic pull.

11. Atelephone receiver comprising a iiexible diaphragm, an armatureconnected thereto, said diaphragm and armature being substantially equalin weight, and pole pieces adapted to influence said armature.

12. A telephone receiver comprising a iiexible diaphragm, an armatureconnected thereto, said diaphragm and armature being substantially e ualin weight, pole pieces adapted to in u'ence said armature, and

means additional to the magnetic pullgfrornit i the pole pieces forurging said armatireii the direction of themagnetic pull to flex thediaphragm, said means exerting a force larger than the maximum magneticpull.

13. A telephone receiver comprising a iexible diaphragm, an armatureconnected thereto, pole pieces adapted to intluence said armature, saidarmature having dimensions so related to the magnetic eld passingthrough the pole pieces4 as to produce substantially a maximum ratio ofmagnetic force to the weight of the armature.

14. A telephone receiver comprising a magnetic circuit of predeterminedmagneto motive force, a branch magneticcircuit in parallel therewith,said first-mentioned circuit having pole pieces adapted to iniuence aiaphragrrn and an armature adjacent sai having a pole disposed adjacentsaid armature and being separated at a point remote from said armatureby a portion ofhigh reluctance from the lrst circuit.

15. A telephone receiver comprising a magnetic circuit of motive force,a branch magnetic circuit in parallel therewith, said rst-mentionedcircuit having pole pieces adapted'toA influence a diaphragm, and anarmature adjacent saidpole pieces, said branch circuit' having a pole inpointrremote from said armature by a portion of high reluctance from theiirst-mentioned circuit, said pole pieces being small in cross sectionwhen compared to the remaining portions of the magnetic circuitassociated therewith.

16. A telephone receiver comprising a magnetic circuit of substantiallyconstant magneto-motive force, a variable'magnetic circuit in paralleltherewith, said circuits pole'pieces, said branch circuit alsopredetermined magnetol larmature spaced therefrom,

proximity to the armature, andn being separated at a having pole piecesin common, and an armature adjacent said pole pieces, said pole piecesbeing spaced a distance not greater than the order of three times thelength of the arma-ture air gap.

17. A telephone receiver comprising a source of magneto motive force,pole pieces of opposite polarity in adjacent positions, an armature inproximity to said pole pieces, and an additional pole piece having oneextremity located between the firstnamed pole pieces, and havingitsopposite extremity .separated from one of said firstnamed pole pieces bya gap of relatively high reluctance.

18. A telephone receiver comprising a source of magneto motive force,pole pieces of opposite polarity in adjacent positions, an armature inproximity to said pole pieces, an additional pole ,piece having one endadjacent the first-named pole pieces, and having its opposite endseparated from one ofsaid pole pieces by a gap of relatively highreluctance, and a closed conductor of relatively low resistance mountedon one of said pole pieces.

19. telephone receiver comprising a magnetic circuit with operatingpoles, an

members urging the armature towards the poles but not in contacttherewith, a diaphragm, a connection between the armature and thediaphragm adjusted to strongly tense the diaphragm and to pull thearmature away from the pole pieces, the tension in said connection beinggreater than the maximum magnetic pull on the armature. In testimony.that I claim the foregoing, I have hereunto set my hand this 18th dayof April, 1922.

LESTER L.` JONES.

